Temperature control of turbine blades on spinning reserve turbines



March 16, 1965 R. c. ROE 3,173,654

TEMPERATURE CONTROL OF TURBINE BLADES on SPINNING RESERVE TURBINES Filed March 14, 1962 2 Sheets-Sheet 1 i9 Y fl l l l 2 also 31 132! 3 i 34 r 39 g g I 37 l i i l i 20 I7 L L 27 .QixQP' 2 a INVENTOR. kg PALPHCPOE.

3,173,654 ADES 0N March 16, 1965 R. c. ROE

TEMPERATURE CONTROL OF TURBINE BL SPINNING RESERVE TURBINES 2 Sheets-Sheet 2 Filed March 14. 1962 INVENTOR. EAL/ H CF05.

Wfikm? A770 RNEYJ.

United States Patent 3,173,654 TEMPERATURE CONTROL OF TURBINE ELADES N SPINNING RESERVE TURBINES Ralph C. Roe, Tenafiy, N.J., assignor to Burns and Rec, Inc., New York, N.Y., a corporation of New Jersey Filed Mar. 14, 1962, Ser. No. 179,743 4 Claims. (Cl. 253-4) This invention relates to temperature control of turbine parts and, more particularly, to the maintenance of such parts at desired temperatures when the turbine is running on spinning reserve.

Those persons skilled in the art will realize the necessity, especially in power plants that must operate through peak periods, of having turbines operate on spinning reserve, that is temporarily running idle with no working steam passing through the turbine but being driven by the electrical end, for example, so as to be immediately available for standby or emergency purposes.

Two basic problems are immediately encountered under such conditions. First, it is desirable that the turbine parts be maintained at temperatures substantially equal to their normal operating temperatures in order that the turbine may be placed, instantaneously, into actual operation under load without an accompanying thermal shock resulting from excessive differences between the various turbine parts and the steam su denly contacting or passing adjacent them. Secondly, if the turbine is operated over a period of time on spinning reserve, then certain turbine components will gradually become overheated due to the windage frictional losses in the rotating elements leading to metal deterioration.

Heretofore, it has been known to operate reserve turbines by passing only that amount of steam through them as is necessary to keep the blades cool, thereby generating a small amount of power. But this practice is expensive and requires a considerable amount of fuel. Additionally, it has been proposed to effect the necessary cooling by means of cooling fluids passing through ducts located inside the turbine blades, but such systems have given rise to expensive and complicated mechanical dilliculties.

Various other means have been employed to reduce the temperature build-up such as blowing air through the turbine casing and circulating exhaust steam through the steam passage, however, these have not been corn pletely satisfactory.

I have conceived by my invention a method and appaartus whereby the necessary temperature control is achieved without the aforementioned limitations that are attendant upon the use of conventional means.

In essence, according to my present contribution, after the turbine is brought up to speed and synchronized on the line, and the steam is shut off leaving in service all necessary accessories such as circulating water and vacuum pumps which are preferably electrically driven, I then inject at selected locations, a small quantity of cooling liquid under pressure, preferably water which may be taken from a condensate hot well, for example, into the turbine blade path in the form of a finely atomized spray to act as a cooling medium, the quantity of water injected at each location being determined by the degree of temperature control required there.

It will be understood that this atomized water will he immediately vaporized by the frictional heat of the rotating blades which operate in near vacuum condition where the power system is of the condensing type, and will return to be condensed by the condenser for re-use. Actually, in such cases the vaporizing temperatures will be relatively low because the water will be vaporized under vacuum maintained by the vacuum pumps. Of

?atented Mar. 16, 1965 course, where non-condensing systems are used, the vaporizing temperatures will be somewhat higher. The vaporization of the water extracts heat from the turbine parts and thereby maintains their temperatures at desired levels.

As an important feature of my invention, the cooling means incorporate multiple thermostatic controls inside the turbine casing and external of the turbine blades by which I am able to maintain the temperatures in the head end of the turbine, and thence down through the turbine stages, at substantially the same temperatures as the operating temperatures of the various turbine parts when operating under load conditions. In this connection, it will be noted that the operating temperature of a turbine generally is not the same throughout, but gradually decreases from the initial stages towards the final stages.

it will be appreciated by those persons skilled in the art that some turbine elements such as the throttle valve, steam chest and interconnecting inlet passages might not receive sufficient heat due to the aforementioned windage and, therefore, heating means may be required to maintain these parts at desired temperatures. Such means may take the form of thermostatically controlled electrical coils embedded in or surrounding said components, or a heat transfer solution such as Hitec, commercially available from the Du Pont Corporation, or a small quantity of hot steam, may be circulated around these various elements. Solutions such as Hitec are particularly desirable for this purpose in plants wherein it is already available for other purposes as contemplated in copending application Serial No. 111,699, filed May 22, 1961, and entitled Heat Storage and Steam Generating Unit.

There has thus been outlined rather broadly the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto. Those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures for carrying out the several purposes of the invention. it is important, therefore, that the claims be regarded as including such equivalent constructions as do not depart from the spirit and scope of the invention.

A specific embodiment of the invention has been chosen for purposes of illustration and description, and is shown in the accompanying drawings, forming a part of the specification, wherein;

FIG. 1 is a plan view of a turbine plant assembled according to the principles of this invention;

FIG. 2 is an enlarged sectional view showing the turbine casing, turbine blades, atomizing spray assembly, and the thermostatic control apparatus;

FIG. 3 is an enlarged plan view of the circular atomizer spray loop and atomizing spray nozzles; and

FIG. 4 is a sectional view taken substantially along the horizontal centerline.

Referring now to the drawings in detail, and more particularly to FIGS. 1 and 4, there is shown, by way of example, a tandenvcompound steam turbine 10 with a double flow, low pressure side 11 and a high pressure side 12. Included therein is a generator 14 which is the common means for spinning a reserve turbine.

Still referring to FIG. 1 there is shown a condenser 15, a condenser hot well 16, a pump 17, and a supply header 19. A small quantity of liquid condensate is led through pipe 20 disposed between the condenser hot well 16 and the pump 17, and is then pressurized to a relatively high pressure by the pump before it is led to the supply header 19 through pipe 21. Leading from the supply header 19 are a plurality of supply lines 22, one of which is shown in detail in FIG. 2. A temperature controlled valve 23 is conveniently positioned in each supply line 22 adjacent its connection with the header 19. Each supply line 22 leads to a circular atomizer spray loop 24 shown in FIG. 3. The supply lines 22 pass through the turbine casing at a convenient point near a set of turbine blades 25 which are to be cooled, as shown in FIG. 2. The circular atomizer spray loops 2.4 are substantially the same diameter as the turbine blade pitch diameter of the turbine wheels located substantially adjacent thereto, respectively, as shown. A plurality of atomizing spray nozzles 25 are disposed on the spray loops 24 and may project axially in the general direction of the turbine blades 25 as shown in FIG. 2, or they ma be directed radially inwardly as shown in HQ. 3, for example. On the inside surface of the turbine casing relatively close to each atomizer spray loop 22 and near the adjacent turbine blading 25 there is a temperature sensing element 27 which is interconnected with and controls the aforementioned temperature controlled valve 23.

When a temperature sensing element 27 calls for more cooling, the respective valve 23 under its control will open to pass the aforementioned high pressure liquid condensate from the supply header 159 through the re spective supply line 22; and thence to the spray loop 24, from whence it passes through the atomizing spray nozzles 26 thereon and is discharged in the form of finely atomized spray.

It will be recalled that the vacuum pumps are kept in operation, wherefore a vacuum of the order of 2 in. Hg. is maintained in the turbine casing. The finely atomized spray discharged from the nozzles will immediately vaporize under the influence of the frictional heat of the turbine parts and the partial vacuum, and will correspondingly cool said adjacent parts.

The present concept includes multiple spray loops 24 along with their attendant temperature sensing elements 27 located at various strategic points throughout the I turbine assembly as indicated at 29 through 39, in FIGS. 1 and 4, for example.

As an illustrative example, assume that a turbine is operating with steam at an inlet pressure of 250 p.s.i.g and an inlet temperature of 600 F. At the end of the first row of blades there would be a temperature closely approximating the initial temperature of 600 F. However, if the turbine idles without steam flow, the temperature would gradually increase to above 600 F. for reasons already mentioned. If the turbine exhausts into a vacuum then the vacuum would extend into this zone. Assuming that the vacuum is 2 in. Hg pressure, with a corresponding saturated temperature of approximately 102 F., then the sprayed water injected by the nozzle 26 would enter at approximately 102 F. and then would immediately vaporize into steam taking heat from the surrounding media. Actually, just enough water would be injected to maintain the 600 F. temperature. In a similar manner, at subsequent turbine stages, the normal operating steam temperature would descend to say 400, 300, 200 F. and so on until the last row of turbine blades is reached. Even here the operating steam temperature is higher than the saturated temperature corresponding to the aforementioned 2 in. Hg pressure, i.e. 102 F. Thus, here the sprayed water injected by the nozzle 26 would also immediately vaporize into steam taking heat from the surrounding media. The water vapor passes through the turbine, through the condenser 15 and ultimately returns to the hot well 16 in liquid form, This example explains the operation at only one turbine inlet pressure and temperature, however, the same principle applies for every case in which the operating temperature exceeds the saturated temperature corresponding to the pressure in the condenser.

This invention is also applicable for use on noncon- Z densing installations. In this case, makeup liquid could be substituted for the aforementioned liquid condensate.

Referring to FIG. 4 numerals 40 and ll show, in general, heating means for the turbine inlet passages 42. These passages may include such elements as the throttle valve, steam chest, steam strainers, steam nozzles, interconnecting piping and easing inlet passages. The heating means could even extend around the entire casing to heat the early stages of the turbine, if necessary, and could take any of the various forms already referred to. It is important that each circuit or heating element 'be provided with thermostatic control in order that the temperature at the corresponding critical turbine location be maintained at a substantially predetermined fixed ternpcrature. The fixed temperature approximates the operating temperature of the respective turbine part or region when running under load conditions so that the turbine may be instantaneously placed into active service when desired without suffering any detriment due to thermal shock.

Although a particular embodiment of the invention is herein disclosed for purposes of explanation, various modifications thereof, after study of this specification, will be apparent to those skilled in the art to which the invention pertains. Reference should accordingly be had to the appended claims in determining the scope of the invention.

What is claimed and desired to be secured by Letters Patent is:

1. In apparatus for maintaining a multistage steam turbine in standby condition for immediate operation, said apparatus comprising a multistage turbine casing, a multistage turbine rotor with blading located within said casing, a hot well in operational relationship with the turbine, a pump, a connecting pipe for liquid flow between the hot well and pump, a spray header, an interconnecting means for liquid flow disposed between the pump and the spray header, a plurality of conduits passing through said turbine casing at points corresponding to the various stages thereof and attached to said spray header, an atomizing spray loop joined to each of said conduits, each spray loop having substantially the same diameter as the adjacent turbine blade pitch diameter, a plurality of atomizer spray nozzles spaced apart on each of said circular atomizer spray loops; individual temperature control means for each of the circular atomizer spray loops including a temperature sensing element located in said turbine casing in proximity to the turbine blades served by the respective loops, a temperature controlled valve located in said conduit disposed between said spray header and said spray loop and responsive to one of said temperature control means to open when the temperature of the turbine stage adjacent its spray header is above normal operating temperature, whereby when the turbine is operating on spinning reserve the turbine parts are maintained at substantially the same temperature as their respective normal turbine operating temperature.

2. In apparatus for temperature control of spinning reserve turbines having parts tending to increase in temperature relatively to their normal operating temperatures at load conditions and other parts tending to cool relatively to their normal operating temperatures at load conditions; a plurality of pressurized hydraulic cooling circuits, atomizer spray nozzles being located in said turbine casing adjacent to said first turbine parts, connecting flow passages between said cooling circuits and the spray nozzles, temperature sensing means located in the turbine casing in proximity to said first turbine parts, filow control means responsive to said temperature sensing means and controlling the supply of liquid to said nozzles, and thermostatically controlled heating means adjacent said other parts, whereby when the turbine is operating on spinning reserve the turbine parts are maintained at substantially the same temperatures as are nor- 5 mal for them under normal operating conditions under load.

3. Apparatus for maintaining a multistage steam turbine in standby condition for immediate operation, said apparatus com-prising means for driving the rotor of said turbine at normal operating speed when steam power thereto is shut 01f, coolant liquid supply means including a plurality of nozzles connected thereto for injecting liquid in spray form into the casing of said turbine at points corresponding to the several stages thereof, individual "alve means associated with said nozzles and operative to control liquid flow through said nozzles and into said turbine, and individual temperature sensing means located within each of the stages of said turbine, said temperature sensing means each being responsive to a rise in temperature above the normal operating temperature in its respective turbine stage to open its respective valve whereby a sufficient quantity of coolant liquid flows through each turbine stage to maintain normal operating temperatures therein.

4. A method for maintaining a multistage steam turbine in standby condition for immediate operation, said method comprising the steps of turning the rotor of said turbine at normal operating speed when steam power thereto is shut ofi, monitoring the temperature within the casing of said turbine at points corresponding to the various stages thereof and spraying a liquid coolant into said turbine casing at each stage where the monitored temperature exceeds the normal operating temperature of the stage.

References Cited in the file of this patent UNITED STATES PATENTS 1,456,652 Rossman May 29, 1923 1,678,066 Lamb July 24, 1928 2,004,777 Bassler June 11, 1935 2,438,998 Halford Apr. 6, 1948 2,780,915 Karen Feb. 12, 1957 2,874,537 Scarborough Feb. 24, 1959 FOREIGN PATENTS 600,838 Canada June 28, 1960 165,991 Great Britain July 14, 1921 

3. APPARATUS FOR MAINTAINING A MULTISTAGE STEAM TURBINE IN STANDBY CONDITION FOR IMMEDIATE OPERATION, SAID APPARATUS COMPRISING MEANS FOR DRIVING THE ROTOR OF SAID TURBINE AT NORMAL OPERATING SPEED WHEN STEAM POWER THERETO IS SHUT OFF, COOLANT LIQUID SUPPLY MEANS INCLUDING A PLURALITY OF NOZZLES CONNECTED THERETO FOR INJECTING LIQUID IN SPRAY FORM INTO THE CASING OF SAID TURBINE AT POINTS CORRESPONDING TO THE SEVERAL STAGES THEREOF, INDIVIDUAL VALVE MEANS ASSOCIATED WITH SAID NOZZLES AND OPERATIVE TO CONTROL LIQUID FLOW THROUGH SAID NOZZLES AND 